Rotary impeller pump



1953 c. J. STUBAU 2,625,112 Y ROTARY IMPELLER PUMP Filed Dec. 24, 1948 T3 30 Z5 27 J3 25 fnz/e'njor'" Carl J Jiubqu Patented Jan. 13, 1953 Cal-1J2. Stubau, Cleveland, Ohio, assignor to Borg- Warner Corporation, Chicago, 111., a corporatien of Illinois.

Application- December 24, 1948, Serial No. 67,111

This invention relatesto pumps; and; more. particularly to. rotary impeller pumps suitable. for high pressure. operation.

Rotary impeller pumps. arev widely used for pumping fluid where. it is desired to. provide a continuous. pumping-"pressure subject to minimum fluctuation. In general. such. rotary" impeller pumps comprise. a rotor mounted on an axis. eccentric to. the axis of the. pump chamber and having aplurality of impellers or vanes slidably mounted in radial slots formed in the rotor. The vanes. are reciprocated in the slots as the rotor-isz rotated. Whilesuch pumps aregenerally satisfactory where. used at; low: pressures, when used at high pressures, the leakage may become excessive, resulting in an appreciable decrease in the efficiency of. the pump.

In accordance with. this invention, ithas been discovered that an important factor contributing to this leakage is the difliculty of maintaining a suflici'ently close fit between the impeller vanes and the sides of the associated slots under all conditions: encountered in operation. Itwill be understood that since these pumps are designed to operate. under varying: load conditions, they will consequently be operated under varying-temper-ature conditions with resultant variations; in the dimensions of the radial slots and the vanes journaled in therotor. Thus, it has been the practice to provide a sufiicient-clearance between the sides of-the slots and the vanes. 50 that any expansion of the vanes which might occur in the operation of the pumpor, conversely; any decrease thewidth of the radial slots, will not causethe vanestosticlt, that is, toseize the sides of the slots. This practice necessarilyrequires acertain loosenessat-normal operating= temperaturesand, consequently the normal efli'ci'encyiof the-pump: is necessarily low; '-Itwill also be apparentthatmachining the slots and-finishing thevanes to; theprecise tolerances required is an. expensive. operation andfurthermore requirescareful fitting: "of the. individual impeller blades: to their respective. slots! It-is. an objectof the. present-invention to provide a..1:otary impeller pumprot' improved: emciency.

It. is a. further. object. of this: invention tarecluce leakage losses. between the. impeller-vanes and the; sides. of: the slots. in the rotor: of'a. rotaryimpeller pump In accordance with one. embodiment of this-invention, spring; loaded; sealing means are provided the rotor adjacent each of? the slotsand are adapted to engage the vanes: in. such. manner 2 Claims. (01. 103%138) 2 as to provide both: a substantially constant bearing pressure and alsoa very effective seal. The combination. bearing and; sealing; means,- as; applied to each; vane. comprises a pair of shoes, of suitable bearing materialilocat edyin oppositely disposed, laterally extending'recesses. formed, in the sidewalls of the. slot and: an-elongated. spring associatedwith each shoe-for. urgingthe shoes into contact with the surface ofthe adiacent side o'f-the. impeller vane.

Other objects and advantages; of, the present invention will be apparent from. the following detailed, description taken inconjuncticn with the drawings wherein:

' .Fig'. 1 -is an axial,. crossesectional view of: a rotary impeller pumphaving combined sealin and bearing means in accordance with this'invention;

Fig. .2 is; an. enlarged, sectional view taken alon the line 2-4 otFig; 1.; and Fig; 3' is an. enlarged'sectional: view taken substantially along the line 3:3 of .Fig. v2.

Referring now to the drawings, it will be seen that. the pump comprises a main. housing; l0 within which. is a casing: ll having; a. cylindrical bore: l2. A. hollow rotor l3 is journaledin. the casing l! and is rotatable. by suitable means (not shown): on an, axis eccentric to: the axis. of the cylindrical. bore l2. Impeller vanes Hand-.15 of conventional. design. are. slidably journaled in. radially extending slots 16 and: lil, respectively, formed; in the rotor [3. In the. operation. of. the pump; the rotation. of the. rotor and t'he; sweepin movement: oi the.- associated. impeller vanes: cause a. diiference in pressure tabs-produced between ports I9 and 20 formed in. the; housing i0". Since the. rotor rotates on an axis eccentrictox that of the bore l2,v rotation. of the rotor causes the: impeller vanes'to be recipricated. intheir respective slots.

Ithasv been. found. in practice that while: such a pump: is quite 'efiicient at low speeds. of operation,. when such. a rotary impeller pump: is. op-

erateri at. higher: speeds to. thereby develop a greater pressure differential. between the. inlet ficien'cy' au'higher-speeds. isjtheincreased friction and; cnnsequentzheati. ,Tlieif'riction, ofic'o'ur'se; in-

termed, is, of course, significant only where thepump is used to pump materials such as gases having a high eflicient of expansion with temperature.

In accordance with this invention, leakage through the slots is reduced to an insignificant quantity and at the same time friction between the sides of the slots and the impeller vanes journaled therein is minimized by providing sealing strips or shoes 23 and 24, respectively, on either side of each of the impeller vanes, the shoes being seated in suitable axially extending recesses 25 and 26, respectively, which are formed in the sides of each of the radial slots i6 and l! in which the vanes are journaled, and which are prefer.- ably oppositely disposed. The shoes 23 and 24 have a generally rectangular cross section, as is evident from Fig. 1, and, as shown in Fig. 2, are as long as the vanes.

The shoes are urged into engagement with the vanes by elongated springs H and 28, respec' vtively, positioned behind the shoes, that is, be-

tween the shoes and the rear walls of the recesses in which the shoes are positioned. The springs are made sufficiently strong to maintain the shoes cating and bearing surface and consequently one having a low coefficient friction, but also a material which will Withstand wear and has high dimensional stability. The use of sealing shoes makes possible the use of materials having lower frictional coeiiicients than it is feasible to use for either the rotor or vanes. Thus, it has been found, in accordance with this invention, that a high lead bronze composition is satisfactory. Such a composition may more specifically comprise on the order of 19 to 23% lead, '78 to 80% 1 copper, and the rest tin.

Referring to Fig. 2, it will be noted that a shoulder 29 is formedadjacent each end of the shoes on the side thereof facing the associated spring to retain the spring in position and to prevent the ends of the spring from touching the end walls 30 and 3| of the pump casing. While an elongated, fiat or leaf type spring of generally sinusoidal or undulated longitudinal configuration has been illustrated, it will be understood that other types of resilient backing means might well be substituted. However, it has been found that the particular form illustrated is well suited to provide a substantially constant pressure and at the same time isreadily assembled in the rotor with the sealing shoes.

By making the over-all height of the shoes slightly greater than the depth of the recesses 25 and 26, it will be evident that the shoes will cooperatively providethe a solesupport for the impellervanes. and the vanes will not engage the sides of the slots at all. This is best shown in Fig. 3.

While in the embodiment illustrated, sealing shoes have been shown positioned on either side of the impeller vanes, where the pump is intended to be operated in only one direction, it is sometimes feasible to omit one set of shoes, thus having only one shoe associated ,with each impeller'blade. The consequent loss of efficiency is not serious for many applications. However, the desired form is that illustrated, since this illustrated form provides also a very effective bearing support for the impeller vane, reducing substantially the area of contact, and thereby the friction losses as well as enabling the use of suitable bearing material as hereinbefore set forth. A further advantage is achieved by the use of the sealing shoes in that the necessity of machining the rotor slots 16 and H to close tolerances is substantially avoided since the spring-pressed shoes automatically establish the minimum clearance required for sealing and at the same time the cooperating bearing pressures on either side of the vanes tend to center the vanes with respect to the slots. Thus the bearing surfaces are reduced to those actually contacted by the sealing shoes.

It has been found in actual tests that where the pump is provided with sealing shoes on either side of the vanes, a quite remarkable improvement in efficiency is obtained. This improvement is due to the improved seal and thereby resultant reduction in leakage and also to the considerable reduction in operating temperature of the pump achieved by minimizing friction. It has also been found that the seal is maintained over a wide range of operating temperatures. For example, in one conventional rotary impeller pump operating at 2250 R. P. M. it was found that the gas discharge was at the rate of 7.4 cubic feet per minute without the sealing shoes and 10.8 cubic feet per minute with the sealing shoes. At the same time it was found that the temperature of the air at discharge was approximately 290 F. without the shoes and 240 F. with the shoes. This reduction in temperature alone accounts for approximately a 5% increase in emciency in addition to the increase in efficiency achieved by virtue of the sealing action, since over the usual operating range of such pumps a decrease in emciency of approximately 1% is incurred for each ten degree rise in discharge temperature.

What is claimed is:

vl. A rotary impeller pump including a rotor having a radially extending slot formed therein, and impeller vanes slidably disposed in said slot, a side wall of said slot having a laterally extending recess formed therein, a sealing shoe in said recess, and resilient means associated with said shoe for urging said shoe into contact with the side of said vane, said shoe comprising an elongated bar having a substantially rectangular cross-section and a shoulder formed adjacent each end for retaining the resilient means in position, the shouldered portion of said sealing shoe having a greater over-all height than the depth of said recess, whereby said shoe projects from said recess under all operating conditions a as to provide a plurality of spaced contacts with the base of said shoe and the adjacent base of said recess whereby said shoe is uniformly urged into contact with said vane.

2. A rotary impeller pump including a rotor having a radially extending slot formed therein, an impeller vane slidably disposed in said slot, a side wall of said slot having a laterally extending recess formed therein, a sealing shoe in said recess, and resilient means interposed between the rear side of said shoe and the base of said recess for urging said shoe into contact with a side of said vane, said sealing shoe having a, shoulder integrally formed therewith adjacent each end l0 of the rear side thereof, said shoulder portion having a greater height than the depth of said recess whereby said shoe projects from said recess under all operating conditions of said pump,

and the length of said shoe being substantially 15 Number equivalent to the length of said vane.

CARL J. STUBAU.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

